Polymer article of manufacture

ABSTRACT

A solid polymeric body comprising a polymer matrix containing a substantially water-insoluble reagent leachable into a substantially hydrocarbon liquid environment, the matrix being reagent permeative and the body preferably having a softening point substantially above that of the temperature of the liquid fluid environment in which it is to be employed. The body is useful for the introduction of an additive reagent into a substantially liquid hydrocarbon such as crude and refined oils.

This is a continuation of application Ser. No. 101,618, filed Nov. 13,1987 (now abandoned) which is a continuation of application Ser. No.758,630, filed July 11, 1985 (now abandoned).

FIELD OF THE INVENTION

This invention relates to a polymeric body useful for introduction of anadditive into a substantially hydrocarbon liquid. More particularly thisinvention relates to a bead containing an additive which is leachableinto an oleaginous hydrocarbon liquid (both crude and refined) and themethod of utilizing the bead to introduce the additive in useful amountsinto the liquid hydrocarbon.

BACKGROUND OF THE INVENTION

The recovery of oil and gas from underground geological formations is ofgreat importance in modern society which uses vast amounts of fossilfuels for its essential energy. The individual well productivitydeclines over a period of time because of a number of factors includingchanges in reservoir fluid characteristics, depletion of reservoirenergy, decreasing permeability of the formation to the oil, the gradualdissipation of the expanding pressure transient, contamination of thewell bore, reduced permeability of the oil through the regionimmediately surrounding the well bore and reduction of the internaldiameter of the well pipe.

The response to the declining productivity was the development ofnumerous techniques which has become collectively known as well workoverand stimulation. The concept of fracturing or formation breakdown hasbeen recognized to play a very important role in the application ofthese oil production enhancement techniques including stimulation,acidizing, water injection and cementing of the formation.

Hydraulic fracturing has found wide usage as a well stimulationprocedure for creating deep-penetrating fractures (both horizontal andvertical) that provide high capacity channels for flow from deep withinthe producing formation to the well as well as for overcoming damagedmatrix permeability surrounding a wellbore. In order to produce gas orliquids from a well at a higher rate following a hydraulic fracturingtreatment, the reservoir must contain enough fluids in place and theformation must not have regions of severe permeability reductionparticularly in regions adjacent to the well. Early experimental work inshallow wells demonstrated that a hydraulically formed fracture tends toheal--that is, to lose its fluid carrying capacity after the partingpressure is released--unless the fracture is propped. Typical proppingagents for retaining the integrity of the fractures are nutshells,plastic beads, aluminum spacers, glass beads, sand and urea prills.

Proppants thus provide a means for meeting the objective of thefracturing which is to increase the well production by preventingcollapse of the formation and resultant decrease in fluid permeability.

Another cause of declining well production is caused by paraffindeposition from the crude oil onto the inner walls of the productiontubing and equipment.

Paraffin is a reservoir produced group of straight-chain alkanes thatcontain more than 15 to more than 80 carbon atoms. The melting point ofthe paraffin increases as the size of the molecule increases. Paraffinis deposited in the form of crystalline solids which may collect on theinterior of the tubing and flowlines, slowly choking off production.Paraffin deposits have also caused the breaking of pump rods. In somecases, paraffin deposits have caused plugging of formations duringstimulation treatments. Paraffin has also been blamed for the difficultyin pumping crude oil at cool temperatures.

One method of handling paraffin deposition is to mechanically remove theparaffin. There are several mechanical methods for removing depositedparaffin from tubing, flowlines and pipelines which include rodscrapers, free-floating pistons, etc. The major advantage ofmechanically removing paraffin is that positive cleaning is assured,however, it is limited due to time and equipment involved, costly andhas the danger and difficulty inherent in retrieving tools lost in thehole during the cleaning operation.

Other methods of cleaning include:

(1) thermal methods, using bottomhole heaters, circulation of hot oil,water or steam, and heat-liberating chemicals; and, chemical includingthe use of paraffin solvents, dispersants and detergents and crystalmodifiers whereby the latter prevents paraffin deposition by disruptingthe nucleation, agglomeration and/or deposition of the paraffin crystalsenvironment. At present the chemical reagent is injected into thedesired location but it can be difficult to supply it uniformly to theoptimum location, for instance in the permeable, oil bearing, mineralformation. Also it is necessary to inject the reagent continuously orrepeatedly since it is soluble in the produced fluid and so is rapidlyremoved from the point of injection.

As indicated it is known to introduce reagents downhole duringfracturing and other well stimulation processes. Traditionally this isdone by forcing a solution of the reagent down the hole and into theformation, whereupon it becomes absorbed onto the formation and isreleased slowly from it. Unfortunately the rate of release is variableand generally is quite fast.

It is known to force beads of ethylene-vinyl acetate copolymers into theformation, but they are generally too large to get into the fracturesformed in the formation and smaller beads would dissolve too rapidly.Also the beads are rather soft.

Another approach to overcoming the paraffin deposition in the recoveryof crude oil is by adding to the oil a polymer having pendant polar andnon-polar moieties, such as a partially hydrolyzed ethylene-vinylacetate copolymer, whereby the deposition of wax from the oil isinhibited (see U.S. Pat. No. 3,693,720 wherein the inhibitor is added tothe crude petroleum oil before the temperature of said oil decreases toa wax-deposition temperature).

It is known from British Patent Specification 1,290,554 to inhibit scaleformation downhole by supplying downhole a solid linear carboxylicpolymer having low molecular weight and in which the carboxylic groupsare neutralized by an alkaline earth or other insolubilizing cation toan extent such that the polymer has a controlled low solubility inwater. It is stated in that specification that water soluble scaleinhibitors may also be supplied downhole with the substantiallyinsoluble polymer.

It is an object of this invention to provide an article and its use toenhance the production of hydrocarbons from geological reservoirs, moreparticularly from fractured formations.

It has been an additional object to devise a composition for providingcontrolled release of a reagent downhole, in a pipeline, in otheroil-containing environments or fluids.

SUMMARY OF THE INVENTION

It has been discovered that it is possible to provide for theintroduction of an additive reagent into a liquid hydrocarbon byproviding solid polymeric bodies each comprising a polymeric matrixcontaining a substantially water insoluble reagent such as a wax crystalmodifier, demulsifier, scale inhibitor, corrosion inhibitor, biocide,ashless dispersant, antioxidant and mixtures thereof. These bodies are,in use, positioned at a location where it is desired to release thereagent into the substantially hydrocarbon fluid and, upon contact withfluid in this location, active reagent is released into the fluid.

Thus in accordance with this invention there is provided a solidpolymeric body comprising a polymer matrix containing a substantiallywater-insoluble reagent leachable into a substantially hydrocarbonliquid environment, said matrix being reagent permeative and the saidbody preferably having a softening point substantially above that of thetemperature of the liquid fluid environment in which it is to beemployed and optimally having a leach rate in which fifty percent of thereagent is leached from the bead in from 3 months to 3 years by thefluid environment.

The object of this invention has been realized in specific form by beadscomprising a copolymeric matrix of methylmethacrylate and methacrylicacid containing the behenyl half ester of a C₂₄ -C₂₈ alkenyl succinicanhydride polymer and having a diameter ranging from 0.2 to 1 mm. Suchbeads when introduced downhole in a hydraulic fracturing operation werefound to inhibit paraffin wax deposition.

DETAILED DESCRIPTION OF THE INVENTION

Each of the solid polymeric bodies may consist solely of a polymericmatrix containing the reagent or may contain a region, generally anouter region, of polymeric material having a lower rate of reagentpermeation than that of the interior region and substantially free ofreagent. The polymer of such an outer shell may be of the same materialas the matrix or may be different, and will be selected having regard tothe release properties required from the polymeric bodies. Matrixcontaining reagent may be of uniform composition throughout its body orits composition may vary, for instance having a different polymercomposition in its outermost portions from its core portion. Byappropriate selection of the polymeric materials for forming the bodiesand the distribution of reagent within the bodies it is possible tocontrol the rate and duration of release of reagent into the fluid whileretaining the physical (structural) integrity of the polymeric matrix.

It is this polymeric property of reagent permeativity which makespossible the transfer of the reagent from the body into thesubstantially hydrocarbon liquid in contact with the surface of thebody. During and after the leaching of the reagent from the reagentpermeative matrix of the body, the polymeric matrix retains itsstructural integrity which is in marked contrast to the approach taughtin Egypt. J. Pharm. Sci., 19 No. 1-4, pages 143-62, 1980 in an articleby A. Kassem et al entitled Formulation and Evaluation of ControlledDissolution Phenobarbitone Macromolecular Products Employing In SituSuspension Polymerization With Methylmethacrylate wherein the reagentcoated beads were compressed into a body which upon reagent dissolutionin the physiological aqueous fluids broke down the body into itscomponent beads thus fully destroying the structural integrity of thecompressed body.

The polymeric bodies are preferably particles. The particle size isgenerally at least 10 microns and preferably at least 50, and usually atleast 100, microns since small particles can be difficult to handle andto position permanently in their desired environment. The particle sizeis generally less than 2 mm and preferably less than 1 mm, since largeparticles also may be difficult to position in their desiredenvironment. Best results are generally obtained with a particle size offrom 50 microns to 1 mm. The particles may have irregular shape andsizes, for instance as a result of having been made by crushing, butpreferably the particles are of substantially spherical or other uniformshape.

When being used in fracturing, the particles preferably have a size andhardness and/or resistance to flow such that they can be used in sandpacking and will not be significantly degraded by the sand. The particlesize distribution will be selected so that a pack of controlledpermeability to fluid flow is formed and such that the particles have acontrolled leach rate as set forth earlier.

The reagent must be substantially water insoluble, and so must partitioninto an organic phase of substantially water-insoluble polymerizablemonomer or monomer mixture in preference to a water phase. The reagentmay be in its active form or it may be in a blocked water-insoluble formfrom which an active form may be released during use and that may bewater soluble.

The reagent may be dissolved in the polymeric matrix but preferably atleast some, and generally substantially all, of the reagent is dispersedin the matrix. The softening point of the matrix should be above ambienttemperatures encountered in use.

The reagent may be any active reagent that is usefully administered toand is soluble in refined or crude oil, or that is any blocked reagentthat is water insoluble but which, upon contact with water or oil, willrelease a water soluble or water insoluble reagent that is useful in thesubstantially hydrocarbon fluid. The reagents are usefully selected fromwax crystal modifiers, demulsifiers, scale inhibitors, corrosioninhibitors, biocides, dispersants, antioxidants and mixtures thereof.

(A) WAX CRYSTAL MODIFIERS

These reagents, usefully introduced in at least a wax deposit inhibitingamount to the refined and crude oil, are represented by oil-solublepolymers having pendant polar and non-polar moieties and oil-solublepolymeric materials having long linear side chains. The oil-solublecopolymers having pendant polar and non-polar moieties are representedby the formula

    [--CH.sub.2 CHR--.sub.m --CH.sub.2 CHX--.sub.p --CH.sub.2 CHY).sub.n ].sub.q

wherein X is a non-polar moiety, Y is a polar moiety, R is hydrogen, analkyl, aryl, aralkyl, or alkaryl moiety, m is 1.5-3, n is 0.1-0.8, p is0.01-0.5, m/(m+n+p) is 0.65-0.97, p/(n+p) is 0.1-0.85, q is 2 to 500,and the molecular weight M_(w) of said polymer is 500-100,000.

The above polymer may typically be a polymer having a molecular weightM_(w) of 500-100,000, preferably 1,000-10,000, commonly 1,500-4,000, say2,000, and characterized by a long straight backbone chain on whichthere may be pendant moieties X and Y.

In the above copolymer, the moiety --CH₂ CHR--_(m) may be derived froman alpha-olefin including ethylene, propylene, butene-1, styrene,3-phenyl-1-propene, octene-1, etc. Preferred alpha-olefins may be the C₂-C₃₀ alpha-olefins and most preferred is ethylene. When the alpha olefinis propylene, the formula --CH₂ CHR--_(m) may be ##STR1## in which R is--CH₃. When the alpha olefin is ethylene, the formula may be --CH₂ --CH₂--_(m). The carbon atoms may bear insert substituents (i.e. in place ofthe hydrogen atoms) including alkyl, cycloalkyl, aryl, alkaryl, aralkyl,etc., moieties.

In the above copolymer, the moiety --CH₂ CHX--_(n) may be derived froman alpha-olefin which bears non-polar moiety X. The non-polar X moietymay be characterized by the fact that it does not contain a hydrogenatom active in the Zerewitinoff test for active hydrogen. Typically, thenon-polar moiety will contain atoms of carbon, nitrogen, sulphur,phosphorous, boron, oxygen, etc. The polar moiety Y may be a moietycontaining carbon, oxygen, sulphur, nitrogen, phosphorous boron or theircongeners. The Y moiety contains a hydrogen atom which is capable ofparticipating in hydrogen bonding. A typically useful wax crystalmodifier is a partially hydrolyzed ethylene vinyl acetate copolymerhaving a molecular weight M_(w) of 1,500-4,000. For a more completedescription of these copolymers reference should be made to U.S. Pat.No. 3,693,720 which by that act is fully incorporated herein and towhich reference should be made.

Another class or wax crystal modifiers are the oil-soluble polymericmaterials having long linear side chains as described in U.S. Pat. No.3,854,893 and include condensation polymers of dicarboxylic acid oranhydride, polyol and monocarboxylic acid; addition polymers ofunsaturated esters, or long chain alpha monoolefins, or copolymers ofsaid olefins with said unsaturated ester; polystyrene acrylated withlong chain fatty acids; and, mixtures thereof. Particularly useful arethe copolymers of C₁₈ to C₄₆ olefin with a C₄ to C₄₄ straight chainalcohol per molar proportion of said dicarboxylic acid. Representativeof these particularly useful copolymers are the esters formed byreaction between the reaction product of an olefin and maleic anhydridewith a long chain (typically C₁₆ -C₂₈) aliphatic alcohol, and mostpreferably the reagent is the behenyl ester of alkenyl succinicanhydride having a molecular weight of from 3000 to 10,000 formed bypolymerizing a C₂₂ -C₂₈ alpha-olefin with maleic anhydride.

Other wax crystal modifiers known for use as pour point depressants arerepresented by: low molecular weight C₁₆₋₂₄ alkyl acrylates andcopolymers with 4-vinyl pyridine, acrylamide, maleic acid, ordimethylaminoethyl acrylate; copolymers of alkyl fumarate and vinylacetate; copolymers of ethylene or other olefins with vinyl alkylate(such as acetate, stearate or laurate); and, copolymers of alpha-olefinswith maleic anhydride or other dicarboxylic group, for instance to formalkenyl succinic anhydride and the reaction products of such materialswith long chain epoxides and long chain alcohols.

(B) DEMULSIFIERS

These reagents which can be introduced into a fractured subterranean oilbearing formation in accordance with this invention are usefullyintroduced to inhibit emulsification of the crude oil with formationwater, water flood injection water and/or water introduced by suchprocesses as steam stimulation. These oil-soluble reagents includepolyoxyalkylene ether and polyalkylene surfactants formed from thealkoxylation of hydrocarbon soluble alkyl phenols, phenolic resins,alcohols, glycols, amines, organic acids, carbohydrates, mercaptans, andpartial esters of polybasic acids.

(C) SCALE INHIBITORS

Since scale inhibitors are water soluble each is introduced into afractured subterranean formation in accordance with this invention asthe reagent in a blocked form such that the reagent upon contact withwater, as by leaching from the polymeric matrix, is converted into awater soluble active form, e.g. as a result of hydrolysis or ionexchange. Suitable blocked forms are fatty acid esters and salts.

Typical examples of blocked scale inhibitors are the salts formed by thereaction of hydrophobic amines with low molecular weight polycarboxylicacids or polyphosphonic acids, e.g. a tri(C₆ -C₁₀ alkyl) ammonium saltof: polyacrylic acid having a M_(w) of from 1,000 to 5,000; ordihexylene triamino pentakis methylene phosphonic acid. It is believedthat the latter reagent also has activity as a corrosion inhibitor.

(D) CORROSION INHIBITORS AND BIOCIDES

Useful reagents which have the property of corrosion inhibition and/orbiocidal activity include both oil-soluble and water-soluble materials.The latter must be incorporated into the polymeric matrix in blockedform.

Typical examples of oil soluble corrosion inhibitors and/or biocides areamines, diamines, fatty amines, polyamines, alkoxylated amines,hydrogenated fatty amines, amides, fatty acid amides, imidazolines, andtrimer acids.

Typical examples of water soluble corrosion inhibitors and/or biocidesare quaternary amines and quaternized imidazolines each of which can beindividually blocked by reaction with oleophilic fatty acids to formwater insoluble salts whereby it becomes useful in the presentinvention.

The reagents may also be materials of value in fuels and lubricatingoils, for instance ashless dispersants or antioxidants. A filter bedthrough which such fluids or oils pass may contain or consist of theparticles containing such reagents.

(E) ASHLESS DISPERSANTS

As used herein, the terminology "ashless dispersant" is intended todescribe the now well-known class of non-metal-containing oil-solublepolymeric additives or the acyl derivatives of relatively high molecularweight carboxylic acids which are capable of dispersing contaminants andthe like in hydrocarbons such as lubricating oils. The carboxylic acidsmay be mono- or polycarboxylic acids and are generally characterized bysubstantially hydrocarbon constituents containing an average of 50 to250 aliphatic carbon atoms.

A preferred class of ashless dispersants are the nitrogen-containingdispersant additives which include mineral oil-soluble salts, amides andesters made from high molecular weight mono- and dicarboxylic acids (andwhere they exist the corresponding acid anhydrides) and various aminesof nitrogen-containing materials having amino nitrogen or heterocyclicnitrogen and at least one amido or hydroxy group capable of salt, amide,imide or ester formation. Usually, these dispersants are made bycondensing a mono-carboxylic acid or a dicarboxylic acid or anhydride,preferably a succinic acid producing material such as alkenyl succinicanhydride, with an amine or alkylene polyamine. Usually, the molar ratioof acid or anhydride to amine is between 1:1 to 5:1.

Primarily because of its ready availability and low cost, thehydrocarbon portion of the mono-, or dicarboxylic acid or anhydride ispreferably derived from a polymer of a C₂ to C₅ monoolefin, said polymermonoolefin generally having between 50 and 250 carbon atoms. Aparticularly preferred polymer is polyisobutylene.

Polyalkyleneamines are usually used to make the non-metal-containingdispersant. These polyalkyleneamines include diethylenetriamine,tetraethylenepentamine, dipropylenetriamine, octaethylenenonamine, andtetrapropylenepentamine. Highly useful mixtures of alkylene polyaminesapproximating tetraethylene pentamine are commercially available.

Representative dispersants are formed by reacting about one molar amountof an oil-soluble polyisobutenyl succinic anhydride with from about oneto about two molar amounts of tetraethylene pentamine or with from about0.5 to 1 moles of a polyol, e.g. pentaerythritol.

It is possible to modify the ashless dispersants generally by theaddition of metals such as boron in order to enhance the dispersancy ofthe additive.

(G) ANTIOXIDANTS

As used herein, antioxidants are oil-soluble oxidation inhibitors andgenerally represented by the additives for lubricating oils whichinclude phenols, amines, sulphurized phenols, alkyl phenothiazines, andzinc dihydrocarbyl phosphorodithioates, e.g. zinc di-n-propyldithiophosphate.

POLYMERIC BODY

The polymeric matrix is reagent permeative and preferably has asoftening point as measured by a temperature-graded hot bar of above 30°C. and most preferably is above 60° C., often up to 120° C. Thecombination of the reagent and the polymeric matrix must be such thatthe reagent is released into surrounding fluid at the desired time andrate either as a result of the fluid permeating through the matrix todissolve the reagent or as a result of the reagent permeating throughthe matrix to dissolve into the fluid, or both.

The polymer of the matrix is preferably formed mainly of acrylic alkylester or styrene or acrylonitrile or a mixture thereof. Suitable acrylicesters are alkyl acrylates and methacrylates where the alkyl groupcontains from 1 to 6 and preferably 1 to 3 carbon atoms. The ester ispreferably a methacrylate and the preferred ester is methylmethacrylate. The polymer is preferably formed mainly of methylmethacrylate or a blend of methyl methacrylate and styrene. Smallamounts of other polymerizable monomers, for instance up to 40%,generally below 20% by weight and preferably below 10% by weight, may beincluded provided they do not deleteriously affect the properties of thepolymer. Other suitable monomers include hydroxyalkyl acrylates andmethacrylates, maleate esters, vinyl esters, dialkylaminoalkylacrylatesand methacrylates and cross-linking monomers such as glycoldimethacrylate. It is particularly preferred to include carboxylicmonomers such as acrylic or methacrylic acid which are useful inmodification of the rate of reagent permeation from the polymeric bodywhen these monomers are incorporated into the monomer mixture, they tendto migrate toward the outer layers of the polymerizing body due to theirhydrophilic nature relative to the reagents. The result is a body havinga lower rate of reagent permeation through its outer region than that ofthe interior region. This approach provides a means of controlling theleach rate of the reagent from the body.

The amount of reagent is generally at least 5% by weight of the totalbody in order to maximize the amount of reagent introduced into thedesired location. It can be difficult to produce bodies containing veryhigh amounts of reagent and so the amount is generally not more than50%, and usually not more than 30%, by weight of the total body. Thepreferred reagent amount is usually 10 to 30% by weight of the totalbody.

The invention has widely diverse applications since it makes possible acontrolled release of reagent into liquids in a uniform manner and overextended time periods. It makes possible the release of certain reagentsfrom previously non- or difficulty accessible and diverse points such asin an oil bearing mineral formation one or more miles underground and inthe flow path of a circulating engine lubricant.

This invention provides a method for the controlled introduction of areagent into a substantially hydrocarbon liquid, generally a circulatingliquid, which method comprises the steps of:

(a) placing solid polymeric bodies, each body comprising a polymericmatrix containing at least one substantially water insoluble reagent ina liquid, generally flowing, substantially hydrocarbon fluid; and

(b) leaching out said reagent from said bodies at a controlled andpredetermined rate into said liquid fluid, said fluid preferablycontaining oil.

In a preferred manner the invention provides a method of recovering acrude petroleum oil containing waxy components, from a reservoir whereinthe oil is at a temperature above its wax deposition temperature whichcomprises:

a. passing a portion of said crude petroleum oil from said reservoir toa first central collection point, i.e. the well bore;

b. passing said oil from said first central collection point to a secondcollection point, i.e. the well head at a temperature below the waxdeposition temperature of said oil whereby the temperature of said oildecreases and passes through a wax-deposition temperature at which thewaxy components begin to precipitate and to deposit on surfaces withwhich said oil comes in contact as it passes to said second collectionpoint;

c. collecting said crude petroleum oil at said second collection point;and,

d. adding to said portion of crude petroleum oil before it passes tosaid first central collection point a wax-depositon inhibiting amount ofa wax crystal modifier reagent by flowing said portion through aparticulate grid of proppant and solid polymeric bodies each bodycomprising a polymeric matrix containing a substantially water-insolublewax deposition inhibitor reagent, said reagent optimally the behenylhalf ester of a C₂₄ -C₂₈ alkenyl succinic anhydride polymer andcontained in said matrix in an amount ranging from 5 to 50 weightpercent of the total weight of said body.

The method of making the bodies of polymeric matrix containingsubstantially water-insoluble reagent involves forming a dispersion inan aqueous medium of particles of reagent and liquid polymerizablematerial and polymerizing the polymerizable material while maintainingthe particles dispersed in the medium. The polymerization results in theformation of a suspension of polymer beads each containing reagent. Thebeads may be filtered or otherwise separated from the aqueous medium.They may be washed and dried.

The aqueous medium will generally include a polymeric stabilizersuitable for suspension polymerization. This is often a hydrophilicpolymer that is swellable in, and usually soluble in, the aqueousmedium. The hydrophilic dispersing stabilizer may be a naturallyoccurring or modified naturally occurring polymer, such as ahydroxyethyl cellulose, or a synthetic water soluble polymer, forinstance polyvinyl alcohol or polyethylene oxide but preferably is asynthetic carboxylic acid containing polymer, most preferablypolyacrylic acid having a molecular weight in the range 1 million to 10million. The amount is generally 0.2 to 5% weight of the water.

In order to obtain uniform and fine distribution of the reagent in thepolymeric matrix, it is necessary for the reagent to be monomer-wettingrather than water-wetting and preferably the reagent is in liquid formduring polymerization of the matrix. It could be introduced as asolution in toluene or other suitable organic solvent but this wouldhave the disadvantage of incorporating solvent in the matrix. Preferablytherefore the reagent is one that dissolves into the polymerizablematerial, if necessary as a result of being heated. For instance it maybe insoluble in the polymerizable material at ambient temperatures butmay become soluble upon heating to a temperature between 50° and 80° C.,in which event the dispersion of the particles of reagent and liquidpolymerizable material is formed at such a temperature. The elevatedtemperature may be such that the reagent is then truly molten or may besuch as to promote solubility of the reagent in the polymerizablematerial.

Preferably a homogeneous blend is formed of the reagent and the monomeror monomers, dispersed into the aqueous medium by stirring andpolymerization is initiated by using an oil soluble thermal initiator.

The following are examples of the invention.

EXAMPLE 1

The behenyl half ester of a C₂₄ -C₂₈ alkenyl succinic anhydride polymerproduced generally according to the procedure set forth for preparationof Polymer B disclosed in U.S. Pat. No. 3,854,893 was supplied as asolution in toluene, and this solvent was evaporated to leave a waxysolid. This wax, i.e. the reagent, was insoluble in methyl methacrylatemonomers at temperatures up to 50° C. A monomer solution containing thewax reagent was formed of 85 g methyl methacrylate, 5 g methacrylic acidand 10 g of the wax by heating all to 65° C., at which temperature thewax dissolved into the monomers. The resultant solution was thendispersed in 200 g water containing 3 g polyacrylic acid (molecularweight about 2 million) as a dispersing stabilizer of the monomerdroplets during polymerization in a one liter enclosed vessel providedwith a stirrer for controlled agitation of the contents within thevessel. Under constant agitation 1 g of azodiisobutyronitrile as thepolymerization inhibitor was added. Suspension polymerization wascontinued with constant agitation for two hours after which time theproduct within the vessel consisted of a suspension of small polymericbeads in the aqueous medium. These beads were separated from the aqueousmedium, washed and dried to give free flowing beads of from 0.2 to 1 mmin diameter with 10% by weight of the waxy ester polymer reagentdispersed in the polymeric matrix.

Since the behenyl ester wax reagent is very soluble in hexane, todemonstrate the retardation of solubility by the invention the producedbeads were stirred in hexane at 35° C and the amount of wax releasedrecorded. The following results were obtained.

    ______________________________________                                        % of Total Wax Released                                                       at 35° C.   Time Hours                                                 ______________________________________                                        40                 1                                                          42                 2                                                          45                 3                                                          49                 4                                                          53                 5                                                          ______________________________________                                    

EXAMPLE 2

When the above process was repeated using 10 g wax reagent (as abovedescribed), 5 g acrylic acid, 5 g methacrylic acid and 80 g methylmethacrylate followed by neutralization with sodium hydroxidedispersion, the beads have a shell containing a high proportion ofsodium polyacrylate and have slower release properties compared to therelease properties of the beads of Example 1 when the polymerizatedispersion was similarly neutralized. In particular, after 5 hours at35° C. in hexane as in Example 1, only 25% of the wax was released.

EXAMPLE 3

To produce a polymeric body according to this invention containing aleachable scale inhibitor, the polymerization mixture will be 85 g ofmethyl methacrylate, 5 g methacrylic acid and 10 g tri(C₆ -C₁₀ alkyl)ammonium salt of a poly(acrylic acid) having a Mw of 1,000 to 5,000. Thepolymerization mixture is to be polymerized under the conditions ofExample 1.

EXAMPLE 4

In order to produce a polymeric body according to this inventioncontaining a leachable corrosion inhibitor reagent, the procedure ofExample 3 is to be followed except that the 5 g of methacrylic acid isreplaced with 5 g of dimethylaminoethyl acrylate, the 10 g of theammonium salt is replaced with 10 g of the equimolar reaction product oftall oil fatty acid and diethylene triamine and the anionic dispersingstabilizer is changed to 3 g of the methyl chloride quaternary salt ofpoly (di-methylaminoacrylate) of about 1 million Mw.

EXAMPLE 5

In order to produce a polymeric body according to this inventioncontaining a leachable demulsifier, the procedure of Example 3 isfollowed except that the following monomer mixture is used: 65 g methylmethacrylate, 20 g styrene, 5 g methacrylic acid and 10 g of anoxyalkylated phenol formaldehyde resin of 2000 Mw where the weightration of ethylene oxide to propylene oxide to resin is 0.5:0.5:1.5.

EXAMPLE 6

In order to produce a polymeric body according to this inventioncontaining a leachable ashless dispersant, the procedure of EXAMPLE 1 isfollowed except that the wax is replaced with the equimolar reactionproduct of polyisobutenyl succinic anhydride having a Mw of about 900and pentacrythritol.

EXAMPLE 7

The effectiveness of the present invention in the inhibition of waxdeposition from a crude oil was shown by comparison of the product ofExample 1 with a solution of the reagent of Example 1 on a crude oil (inwhich the aforesaid reagent has shown measurable wax depositioninhibiting activity) using the following procedure. 0.03 weight parts ofactive ingredient was introduced into 100 weight parts of crudepetroleum oil. The mixture was placed within a test cell containing apreweighed, removable standard water chilled deposition steel plate, astirrer thermometer, and an electrical heater. The test cell was placedin an insulated bath together with an identical reference cellcontaining the reagent solution treated base crude oil. The temperatureof the oils in both cells was maintained at 2° to 5.5° C. above theknown cloud point temperature of the oil (as determined by ASTMD-97-57). The test was continued for 6 hours and then each depositionplate was removed, and weighed. The amount of wax deposit on each platewas for measureable activity the same.

EXAMPLE OF USE

The solid particles of the present invention can be used to inhibitparaffin deposition from waxy crude oils by placing them downhole withthe proppant sand during the course of a fracturing operation.

To effect the placement of the particles of the invention a fracturingoperation is carried out as follows. A fracturing fluid is prepared bygelling a 2% solution of potassium chloride with hydroxy propyl guarcross linked with a transition metal complex. As the fluid is pumpeddownhole 8 lbs/1000 gals of 20-40 mesh sand mixed with 5% of the beadsof the invention are added to serve as a proppant in the fracturesformed in the producing formation. Pump pressure is increased above thefracture gradient of the rock formation and the fluid carries theproppant mixture into the fractures. The well is then shut in for 24hours to allow the guar gel to degrade to a low viscosity solution. Thewell is allowed to flow back and the fracturing fluid is recoveredleaving the proppant mixture of sand and polymer beads behind.

As the produced oil flows through the proppant pack past the beads thewax deposition inhibitor slowly leaches out and deposition is inhibitedin the well bore and the flow lines as the oil cools and production ismaintained at a high level without wax blockage.

As used herein % by weight is based on the total weight of the body,polymer composition, water or bead, respectively.

What is claimed is:
 1. A particulate treating material for anenvironment including a hydrocarbon liquid, each particle of thematerial comprising:(a) a body composed of a copolymer prepared bysuspension polymerization of a monomer mixture of(i) a first monomerselected from the group consisting of acrylic alkyl esters, styrene,acrylonitrile, and mixtures thereof; (ii) a second monomer selected fromthe group consisting of methacrylic acid, hydroxyalkyl acrylates,hydroxyalkyl methacrylates, dialkylaminoalkyl acrylates,dialkylaminoalkyl methacrylates, and mixtures thereof;said copolymerbeing insoluble in hydrocarbon liquid, having a softening point above30° C., having structural integrity, internal porosity, and a particlesize of at least 100 microns and less than 2 millimeters; and (b) areagent soluble in hydrocarbon liquid and being dispersed in said body,said reagent constituting at least 5 wt % and not more than 30 wt %based on the combined weights of the body and reagent, said reagentbeing added to, and soluble in, the monomer mixture and insoluble in thecopolymer and being selected from the group consisting of scaleinhibitors, corrosion inhibitors, biocides, foamers, and oxygenscavengers, and being leachable, at least in part, by a hydrocarbonliquid permeating said body, said body retaining its structuralintegrity without the reagent.
 2. The particulate treating material ofclaim 1 wherein the first monomer is selected from the group consistingof alkyl acrylates and alkyl methacrylates wherein the alkyl groupcontains from 1 to 6 carbon atoms.
 3. The particulate treating materialof claim 2 wherein the first monomer is methyl methacrylate.
 4. Theparticulate treating material of claim 1 wherein the monomer mixturefurther includes an effective amount but less than 10 wt % of acrylicacid or methacrylic acid based on the weight of the monomers to providean outer region of reduced permeability compared to the particle regionwithin the outer region.
 5. The particulate treating material of claim 4wherein the monomer mixture comprises a major weight proportion of thefirst monomer.
 6. The particulate treating material of claim 5 whereinthe first monomer is methyl methacrylate.
 7. The particulate treatingmaterial of claim 1 wherein the first monomer is a blend of methylmethacrylate and styrene.
 8. A particulate treating material fortreating environments containing a hydrocarbon liquid wherein eachparticle comprises a solid copolymer body of structural integrity andhaving a particle size between 100 microns and 2 millimeters and asoftening point above 30° C., said copolymer body being formed byaqueous suspension polymerization of(a) a monomer mixture comprising(i)a first monomer selected from the group consisting of alkyl acrylicesters, styrene, and mixtures thereof, (ii) a second monomer selectedfrom the group consisting of a methacrylic acid, hydroxyalkyl acrylates,hydroxyalkyl methacrylates and dialkylaminoalkyl acrylates,dialkylaminoalkyl methacrylates, and mixtures thereof; and (b) awater-insoluble, hydrocarbon liquid-soluble reagent dissolved in themonomer mixture, and being insoluble in the polymerized copolymer,whereby the reagent is dispersed throughout the copolymer body, saidreagent being leachable from the body by the hydrocarbon liquid, atleast in part, permeating the body, each body retaining its structuralintegrity with the reagent leached therefrom.
 9. The particles of claim8 wherein the first monomer is methyl methacrylate.
 10. The particles ofclaim 8 wherein concentration of the second monomer is sufficient toproduce the copolymer but does not exceed 20 wt % of the copolymer. 11.The particulate treating material of claim 8 wherein the monomer mixturefurther includes an effective amount but less than 10 wt % of acrylicacid or methacrylic acid based on the weight of the monomers to providean outer region of reduced permeability compared to the particle regionwithin the outer region.
 12. The particles of claim 8 wherein thereagent is the behenyl half of a C₂₄ -C₂₈ alkenyl succinic anhydridepolymer.